1. Field of Invention
The present invention relates to a scanner and a scanning method. More particularly, the present invention relates to a multiple-field sensor for image scanning.
2. Description of Related Art
Due to the rapid development of multimedia technologies, image processing speed and clarity have become an important consideration in the selection of a scanner by users. However, a scanner operates according to light reflected from a document. Hence, outside light or any irregular dispersion, diffraction may lead to certain degree of distortion for a scanned image. In addition, limitations in the manufacturing of sensors also contribute to the production noise signals that further distort the image.
An attempt to deal with image distortion problem has been proposed in the Taiwan Patent No. 385608. In the invention, a sensor is used to scan a document a multiple of times to obtain a multiple of scanned images. Thereafter, the scanned images are averaged to reduce the amount of distortion to the actual image. However, this and similar type of designs require multiple scanning and the sensor has to shuttle forward and backward many times. Hence, the scanning is time-consuming and highly inefficient.
In brief, common defects of conventional scanning techniques include:
1. The scanned image is likely to be distorted if noise signals contained within the image are untreated; and
2. If the scanned image is treated by scanning the same documents a few times using the same sensor, the sensor has to shuttle many times leading to time wastage and hardware control problems.
Accordingly, one object of the present invention is to a multiple-field sensor for a scanner suitable for scanning a document. The scanner includes a multiple-field sensor, an average accumulator, and a block of memory. The multiple-field sensor has a plurality of sensing lines for each color channel. Each sensing line picks up a portion of image signal from the document during scanning. The sensing lines scan the same portion of the document to produce corresponding image signals. The average accumulator averages the image signals obtained from the sensing lines of the same color channel to produce an average image signal. The block of memory is used as a storage area for image signals in general and the average image signal in particular. In addition, the scanner further includes a memory read/write address controller. The memory read/write address controller supplies addresses for storing and retrieving the image data and the average image data to and from the memory blocks.
The invention also provides a scanning method that utilizes a multiple-field sensor. The multiple-field sensor has a plurality of sensing lines corresponding to each color channel. Each sensing line can be used for scanning a document to obtain a corresponding portion of the image signal. First, the scanning lines sequentially scan an identical portion of the document to obtain a plurality of image signals. Thereafter, the image signals are averaged to obtain an average image signal. Finally, the average image signal is output. In addition, the step of obtaining an average image signal includes first storing the image signals and then adding up the image signals. Lastly, the sum is averaged to obtain the average image signal. Furthermore, the steps for obtaining an average image signal by the scanning method of this invention are executed in a pipeline mode.
In brief, a multiple-field sensor is used to obtain a multiple of image signals at the same time. The image signals are then accumulated and averaged in a pipeline mode of operation. Hence, image distortion due to noise interference is reduced without increasing scanning time.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.